Post-tensioning apparatus and system for structures

ABSTRACT

The present invention pertains in general to post-tensioning apparatus and systems surrounding the fabrication and repair of concrete and other construction materials. The present invention surrounds apparatus and system directed to the post-tensioning for reinforcement of existing and new concrete structures through the application of tensile forces between two attachment points anchored to the structure to be mended.

CROSS REFERENCE TO REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication 62/253,681 entitled “Post-Tensioning Apparatus and Systemfor Structures” filed on Nov. 11, 2015, the entire contents of which areincorporated herein by reference in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention pertains in general to post-tensioning apparatusand systems surrounding the fabrication and repair of concrete and otherconstruction materials. The present invention surrounds apparatus andsystem directed to the post-tensioning for reinforcement of existing andnew concrete structures through the application of tensile forcesbetween two attachment points anchored to the structure to be mended.

BACKGROUND OF THE INVENTION

The field of concrete installation and maintenance, particularlysurrounding structural or load bearing concrete, requires sitepreparation and formula of mix to create the desired preparation.Although mechanically strong in compression, concrete is relatively weakin tensile and bending loads and is subject to cracking and breakageunder such conditions.

Practices including techniques of post-tensioning, which involves thepre-stressing of steel tendons within the concrete form to account forits relative weakness in tension. This practice is often used ininstallation for purposes such as commercial and residentialconstruction where beams, floors and bridging components must span alength exceeding longer than practical with ordinary reinforcedconcrete.

Although the practice of post-tensioning aims to pre-load concrete andplace it under a resting compressive load to counteract tensile andbending loads to mitigate mechanical failures. However, uncontrollablevariables such as frost heaving, ground movement, erosion, waterinfiltration and others compromise the structural integrity of concreteand can cause cracking and mechanical failure of the structure of theconcrete installation.

Due to the costly or nature or logistical impossibility of thereplacement of concrete installations, many solutions aim to repairconcrete after mechanical failure. Although it may seem sensible toreplace a concrete installation in some situations, it will beappreciated that even the wholesale demolition and reinstallation of theconcrete may not guarantee against failure in the future.

Cracks in concrete are caused due to the mechanical failure of theconcrete in a localized area due to a possible variety of problems withthe installation. For this reason, tensioning may be desired inscenarios such as the cross-linking of independently poured concreteinstallations or providing tension in “post-tensioning” to repair aconcrete installation using tensile strengthening features. Theapplication of metal structure for the tensile reinforcement istypically placed across a mechanical failure zone such as a fissure orcrack where the concrete installation has mechanically failed.Post-tensioning typically involves preloading of a metal structure priorto adding more concrete to reinforce the repair.

SUMMARY OF THE INVENTION

Some solutions aim to fill the crack with a bonding adhesive or cementto repair the concrete. However, the lack of strength afforded bycements, often referred to as hydraulic cement, proves problematic. Whenconsidering the structural integrity of a concrete installation, thecost of repeated failure depends upon the application of the concrete.And cement patches have a high risk of repeated failure due to weak bondand structural integrity of the cement.

Other solutions to the mechanical failure of concrete resulting incracks is addressed through internal metal stitching as proposed by U.S.Pat. No. 5,476,340, ('340), and U.S. Pat. No. 5,771,557, ('557),incorporated herein by reference, to Contrasto. Constrasto '340discloses a method surrounding the use of apparatus '557 to bridge acrack using a series of cuts across a crack, inserting metal structure,and making additional cuts across the previous cuts and metal structureto add cross structure in the form of metal brackets prior to theaddition of filler material. Contrasto '340 fails to provide any methodof tension application to the concrete.

Constrasto '557 aims to provide increased localized tensile strength forthe concrete around a crack. The higher ductility of steel as comparedto concrete does not prevent the movement of the concrete beyond afailure threshold and therefore cannot prevent further cracking in thelocalized region and Contrastro '557 fails to provide the ability topre-tension the structure or provide post-tensioning to the concretestructure.

Some solutions aim to address failed concrete by placing devices acrosscracks due to mechanical failure in efforts to provide post-tensioningby preloading metal members spanning across the crack. These metalmembers comprise plates with a post at either distal end affixed to oneside that are inserted into pre-drilled apertures for anchoring. Themetal members are then tensioned using wedge or cam based mechanisms totension the metal member after the posts have been inserted into theconcrete. These tensioning mechanisms, however, are limited in travel.If the apertures created for the posts are spaced too far apart, theuser may not be able to install the metal member. If the aperturescreated for the posts are too close together, the user may not be ableto tension the metal member as prescribed.

The present invention relates to a post-tensioning apparatus and systemproviding functionality of post-tensioning to existing structures. Thepresent disclosure relates to the repair of concrete structures but isnot limited to such application. Embodiments of the invention permit theapplication and adjustment of a modular post-tensioning apparatusincluding at least two attachment features interconnected by at leastone tensioning mechanism. The modularity of the apparatus surrounds theability to select and use different attachment features based upon thelocation, substrate, desired tensioning properties and other relevantvariables in the tensioning of a structure.

In certain embodiments of the present invention, a modular apparatus andsystem provides tension to existing structures, such as an existingconcrete installation, where it is desired to provide post structuralreinforcement.

Embodiments of the apparatus provide tensile strength across amechanical failure zone without further tensioning of the apparatus.However, tensioning the apparatus preloads the apparatus to resolvetolerances or gaps between the apparatus and the points of applicationwithin a structure to which it is applied. Tensioning the apparatus alsoplaces the apparatus in tension and compresses the structure betweenattachment features applied to the structure. This also mitigatestensile forces bearing on the concrete, as concrete is typically weakerin tension than in compression.

Certain embodiments of the present invention comprise at least twotension application components interconnected by one tensioningmechanism. Once the tension application components are applied to thestructure, the tensioning mechanism is actuated to apply a tensile loadto the tension application components, placing the apparatus in atensile state.

Tension application components translate forces from the tensioningmechanism to the structure by attaching to the structure, such as aconcrete installation. Each tension application component may also beattached to one or more application points. These application points maybe on a singular structure or spanning two separate structures. It willbe appreciated that the tension application components may comprise avariety of forms including, but not limited to, a post-like device,hook, loop and/or plate with attachment features for attachment to astructure. In certain embodiments, the apparatus permits modular use ofa variety of tension application components where the apparatus may beused with two tension application devices of similar or dissimilar size,shape or form. It will be further appreciated that application pointsmay comprise apertures in the structure, other features within theconcrete or hardware pre-affixed to the concrete.

In certain embodiments, a tensioning mechanism comprising two axiallyaligned threaded female features, one having standard clockwisethreading and the opposing exhibiting counter-clockwise threading, isreferred to as a turnbuckle. In such an embodiment, the tensionapplication components have a cylindrical cross-section with a length ofscrew threading at a proximal end to engage with the threaded femalefeatures of the tensioning mechanism. Furthermore, the distal section ofthe tension application component has as bend, which provides apost-like form to allow the application of force upon an existingstructure. A structure may also be prepared by creating an aperture inthe structure where one can place the tension application component toapply force on the structure.

It will be appreciated that a tensioning mechanism may comprise aturnbuckle. The tensioning mechanism may also comprise a rotationaldevice with a set of indexed features radially around the rotationaldevice in which a pawl, cog, or tooth engages to allow motion in onedirection only, such as a ratchet, or a geared mechanism such as arack-and-pinion or worm gear.

Certain embodiments of the present invention are directed to the repairof a concrete structure where a fissure or crack has occurred. Thesurface is prepared by creating plurality of apertures with at least oneaperture being on a first side of a fissure or crack, and at least oneaperture being on a second side of a fissure or crack. The apertures arepositioned at a distance that generally corresponds to the length of theapparatus prior to actuation of the tensioning mechanism which shortensthe apparatus. The distal ends of first and second tension applicationcomponents are then inserted into the corresponding apertures of theprepared surface. Tension can then be applied by actuating thetensioning mechanism, creating post-tensioning in the area surroundingthe crack or fissure.

In certain embodiments, a tension application component is used to applya tensile load across a portion of a structure. The tension applicationcomponent comprises an attachment end configured to engage with atensioning mechanism. The attachment end engages the tensioningmechanism at a proximal end of the tensioning application component. Thedistal end of the tension application component has a feature such as anaperture or hook-form configured to engage with features installed inthe structure. Such features which include, but are not limited to apost or rebar affixed to the structure.

Certain embodiments of the present invention comprise a tensioningapplication component that engages with the tensioning mechanism. Theproximal end of the tension application component has an attachmentfeature configured to engage with the tensioning mechanism. The distalend of the tension application component is configured to engage theapertures within a prepared surface or extents of an existing structurewith a plurality of post-like features. Having a plurality of post-likefeatures distributes the load of the tensioning apparatus across alarger area. The distribution of forces allows the installation of apost-tensioning apparatus with structures having limited structuralstability rather than an apparatus with a more concentrated loadingwhich may risk further damage to the structure to be repaired. Ascenario in which a user may want to use more than one post-tensioningapparatus, the plurality of post-like features allows the use of fewerpost-tensioning apparatuses over a given length of a fissure or crack toachieve stronger structural stability.

Certain embodiments have a tension application component. In certainembodiments, the tension application component comprises a plate-form.The plate-form affixes to a structure to apply tensile load to thestructure at the desired location. The plate-form can be affixed bywelding or using at least one threaded fastener, masonry anchor or othermethods known to those skilled in the art. The plate-form may furthercomprise a fixation point such as a loop or hook to allow the engagementof a tension application component. It may be desired to affix theplate-form to the structure using a plurality of fasteners or anchors todistribute tensile loading across a larger area of concentration on thestructure. This distributed loading can also provide tensile strengthbetween independent structures where other types of tension applicationcomponents cannot. In contrast, post-like forms create a higherlocalized concentration of stress. Furthermore, the use of plate-formsmay allow the post-tensioning between adjacent structures that are notcoplanar such as adjacent planar structures disposed at not offer thenecessary structural stability to provide tension between independentstructures.

In certain embodiments, a tension application component has a plate-formhaving at least one aperture. The tension application component includesan engagement feature extending outward from the surface of theplate-form. The engagement features can engage with a tensioningmechanism, including through the use of a threaded male component, thethreaded male component typically being axially parallel to the bore ofthe aperture in the plate-form. In such an embodiment, a tensionapplication component can be attached to a first surface at an angle,typically orthogonal, and attached to a second surface. This allowspost-tensioning across a crack or fissured that has occurred proximal toa corner where two sections of a structure meet at an angle.

Certain embodiments of the present invention comprise a tensionapplication component having at least two parallel post structures. Thetwo parallel post structures are disposed at an angle from a connectingbody. The tension application component has an aperture, located medialto the post structures. The aperture is also typically axially parallelto the post structures. The tension application component distributesthe load applied to the structure and provides a post-tensioning effectto a larger area. In certain embodiments, the tension applicationcomponent has a post feature attached to a tensioning mechanism, wherethe post feature is disposed through the medially located aperture.

In certain embodiments of the invention, the apparatus comprises atensioning mechanism having a consistent cross-sectional profile. Thetensioning mechanism can have female threaded features at its distalends. The threaded receptacles have opposing threading direction. Thus,when engaged with rotationally constrained male threaded features, theopposite threading direction allows both male threaded features to bedrawn toward the center of the tensioning mechanism when rotated in afirst direction and forces the male threaded features away from centerwhen rotated a second direction, opposite the first direction.Alternatively, it will be appreciated that the tensioning mechanism mayhave male threaded features and the tension application components havefemale threaded features.

In certain embodiments, the tensioning mechanism has a torqueapplication feature. The torque application feature actuates thetensioning mechanism by applying rotational forces to tensionapplication components. The torque application feature may havedifferent individual forms or a combination of forms as known to thoseskilled in the art. The profile of the tensioning mechanism may haveforms including but not limited to elliptical, circular, hexagonal,octagonal or square.

In certain embodiments, the external profile of the tensioning devicehas a form with parallel exterior surfaces, such as a square, hexagonalor octagonal form. The external profile may be used for the applicationof torque with a tool such as a wrench or other standard torque applyingtool.

In certain embodiments, the tensioning mechanism has at least oneaperture. The aperture passes through the tensioning mechanismperpendicular to central axis of the mechanism typically intersectingthe central axis. The aperture allows for torque application through theuse of a rod or other shaft-like object inserted into the aperture.After torque application it may be desired to dispose a rod in theaperture to prevent counter-rotation by engaging the rod with thestructure, such as concrete, to which an apparatus comprising atensioning mechanism is applied. It will be appreciated by those skilledin the art that such apertures are typically in a medial section of thetensioning mechanism. Furthermore, it may be desired to have a pluralityof apertures. The additional apertures can be angularly displaced fromother apertures such as on 45-degree or 90-degree increments that allowfor easier adjustment of the tensioning mechanism in tighter locations.The apertures may be coplanar to the axis of the central axis. Incertain embodiments, the apertures may be located on offset yet parallelplanes that are perpendicular to the central axis of the tensioningmechanism.

Embodiments of the present disclosure may be used in a system comprisingat least one tensioning mechanism and at least two tension applicationcomponents. Furthermore, different tensioning components may be usedinterchangeably with a tensioning mechanism to allow systemcustomization for each application.

BRIEF DESCRIPTION OF FIGURES

FIG. 1A—A top view of a post tensioning system

FIG. 1B—A side view of a post tensioning system

FIG. 2—A side view of a turnbuckle embodiment of a tensioning mechanism

FIG. 3—A side view of a tension application component

FIG. 4A—A side view of a tension application component

FIG. 4B—A top view of a tension application component

FIG. 5A—A top view of a post tensioning system

FIG. 5B—A side view of a post tensioning system

FIG. 6A—A perspective view of a tension application component

FIG. 6B—A top view of a tension application component

FIG. 6C—A side view of a tension application component

FIG. 7A—A top view of a post tensioning system

FIG. 7B—A side view of a post tensioning system

FIG. 8A—A bottom view of a tension application component

FIG. 8B—A side view of a tension application component

FIG. 8C—A top view of a tension application component

FIG. 9A—A perspective view of a post tensioning system

FIG. 9B—A side view of a post tensioning system

FIG. 9C—A front view of a post tensioning system

FIG. 10A—A side view of a tension application component

FIG. 10B—A top view of a tension application component

FIG. 11—A perspective view of a tension application component

DETAILED DESCRIPTION

In certain embodiments of the present invention, a modular apparatus andsystem provides tension to existing structures, such as an existingconcrete installation, wherein it is desired to provide structuralreinforcement. Tensioning may be desired in many scenarios such as thecross-linking of independently poured concrete installations orproviding tension in “post-tensioning” to repair a concrete installationusing tensile strengthening features. The application of metal structurefor the tensile reinforcement is typically placed across a mechanicalfailure zone such as a fissure or crack where the concrete installationhas mechanically failed.

An apparatus 100, as shown in FIGS. 1A and 1B, embodying the inventiveprinciples of the invention comprises at least two tension applicationcomponents 101 a and 101 b and one tensioning mechanism 102 disposed andattached therebetween. When the tension application components 101 areconstrained, the actuation of the tensioning mechanism 102 appliestensile force to the tension application components 101 resulting inplacing the apparatus in a tensile state. Certain embodiments of such anapparatus may comprise an overall length of 30.5 cm (12 in).

The tension application component 101 translates forces from thetensioning mechanism 102 to the structure by attaching to a structure,such as a concrete installation. The tension application component 101may also be attached to two or more independent elements or structures.It will be appreciated that the tension application components 101 maycomprise a variety of forms including, but not limited to, a post-likedevice, hook, loop and/or plate with attachment features for attachmentto a structure. In certain embodiments the apparatus 100 permits modularuse of a variety of tension application components wherein the apparatusmay be used with two tension application devices of similar ordissimilar size, shape or form.

In certain embodiments of the apparatus, as shown in FIG. 2, atensioning mechanism 102 comprises two axially aligned threaded femalefeatures, 201 a and 201 b, having opposing threading at first and seconddistal ends of the tensioning mechanism 102. For instance, an embodimentof a tensioning mechanism 102 may comprise 201 a having standardclockwise threading and the 201 b having counter-clockwise threading.This configuration of tensioning mechanism 102 is commonly referred toas a turnbuckle. In certain embodiments a tensioning mechanism 102comprises a length of 10.2 cm (4.0 in) and diameter of 15.875 mm (0.625in) In such an embodiment the tension application components 101 a and101 b, as shown in FIG. 3, have a cylindrical profile with a length ofscrew threading, 301 a and 301 b, at a proximal end 302 to engage withthe threaded female features, 201 a and 201 b, of the tensioningmechanism 102. Furthermore, the distal section 303 of the tensionapplication component has a bend which provides a post-like form 304 toallow the application of force upon an existing structure or apertureprepared in a structure for the placement of the tension applicationcomponents 101 a and/or 101 b. It will be appreciated that the bend inthe tension application components 101 a and/or 101 b may comprise aplurality of angular bends typically totaling at least 90-degrees. Incertain embodiments the female threaded features as illustrated by FIG.2, the threaded female features 201 a and 201 b have screw threadinghaving a lead of 1.5875 mm (0.0625 in) and a diameter of 9.525 mm (0.375in). It will be appreciated to those skilled in the art that lead,surrounding male threaded features, indicates the axial travel for asingle revolution of the screw thread. In such an embodiment, the screwthreading 301 a and 301 b, seen in FIG. 3, also have screw threadinghaving a lead of 1.5875 mm (0.0625 in). Such embodiments may bedesignated with ANSI thread designation as ⅜-16 per ANSI/ASME B1.1-1989(R2001). Certain embodiments of a post-like form 303 as seen in FIG. 3,comprises a length of 44.45 mm (1.75 in) and diameter of 9.525 mm (0.375in). It will be appreciated that other embodiments may have post-likeforms of different lengths. It will be appreciated that a tensionapplication component 303, shown to have a matching cross-section to themale threaded features 301 a and 301 b, are not limited to a roundcross-section or dimensions matching that of the male threaded features301 a and 301 b. It will be further appreciated that the threadingassociated with the male threaded features 301 a and 301 b, seen in FIG.3, and the female threaded features 201 a and 201 b may comprisethreading larger or smaller than embodiments described herein. Certainembodiments of a tension application feature 101 a and 101 b maycomprise a length of 12.7 cm (5.0 in).

It will be appreciated by those skilled in the art that apost-tensioning device may be made of a steel alloy designated as a hotrolled and proof stressed alloy steel conforming to ASTM A722 CAN/CSA(G279-M1982). It will be further appreciated that certain embodimentsmay be made of a steel allow such as AISI 1144, sometimes referred to byan associated trade name of Stressproof®. AISI 1144 steel is appreciatedto those skilled in the art as a is a carbon-manganese grade steel whichis severely cold worked to produce high tensile properties.

Certain embodiments such as those shown in FIGS. 1A-3 are directed tothe repair of a concrete structure where a fissure or crack has occurreddue to mechanical failure. The surface is prepared by placing aperturesin the concrete on either side of the fissure or crack. The aperturesare positioned at a distance that generally corresponds to the thelength of the apparatus 100 with attached tension application components101 a and 101 b prior to actuation of the tensioning mechanism 102 whichshortens the mechanism. The distal end 303 of tension applicationcomponents 101 a and 101 b, such as the those shown in FIG. 3, into thecorresponding apertures of the prepared surface. Tension can then beapplied by actuating the tensioning mechanism 102 to creatingpost-tensioning in the area surrounding the crack or fissure.

In certain embodiments of the apparatus as shown in FIGS. 4A-5C, atension application component 401 applies tensile load across a desiredstructure. The tension application component 401 comprises an attachmentfeature 402 at a proximal end 403 for engaging with a tensioningmechanism and an aperture 404. The distal end 405 has a tensionapplication feature 404, such as an aperture or hook-form, configured toengage with features installed in the structure. Such features include,but are not limited to, a post or rebar, affixed to the structure.

Certain embodiments of the invention, as shown in FIGS. 6A, 6B, 7A, 7Band 7C, comprise a tension application component 601 that engages with atensioning mechanism 102. A proximal end 603 of the tension applicationcomponent 601 has an attachment feature 602 configured to engage withthe tensioning mechanism 102. The distal end 605 of the tensionapplication component 601 is configured to engage the apertures of aprepared surface or the edges of an existing structure by having aplurality of post-like features 604. Having a plurality of post-likefeatures 604 distributes the load of the tensioning mechanism 102 acrossa larger area. The distribution of forces allows the installation of apost-tensioning apparatus 601 in conjunction with structures that cannotoffer structural stability for an apparatus with a more concentratedloading. Certain embodiments of a tension application component 601 asseen in FIG. 6A-C has a two parallel post-like features 604interconnected such that the post like features are separated by adistance of 8.89 cm (3.5 in). In the scenario which a user may want touse more than one post-tensioning apparatus 601, the plurality ofpost-like features 604 allows the use of fewer post-tensioningapparatuses 601 over a given length of a fissure or crack to achievestronger structural ability. Certain embodiments of an aperture 404 asseen in FIG. 4, comprise a length of 19.05 mm (0.75 in) and width of12.7 mm (0.5 in). Certain embodiments of a tension application feature405 as seen in FIGS. 4A and 4B has a length of 59.18 mm (2.33 in), widthof 31.75 mm (1.25 in) and thickness of 9.525 mm (0.375 in).

Certain embodiments have a tension application component. Such as thoseshown in FIGS. 8A, 8B, 8C, 9A, 9B and 9C, a tension applicationcomponent 801 comprises a plate-form 802, the plate-form 802 having atleast one aperture 803. The plate-form 802 affixes to a structure,typically using at least one aperture 803 in the plate-form 802. Theplate-form 802 may be affixed to the structure through an aperture 803.Fixation strategies include the use of threaded features, masonryanchors and other methods known to those skilled in the art. This allowsthe application of tensile load to the structure at the desiredlocation. The plate-form 802 further comprises and engagement features,such as a threaded male component 804 extending outward from the surfaceof the plate-form, typically axially parallel to the bore of an aperturein the plate-form. This engagement feature is configured to engage witha tensioning mechanism 102. In such an embodiment, a tension applicationcomponent 801 can be attached to a first surface at an angle to,typically orthogonal, and attached to a second surface. This allows posttensioning across a crack or fissure that has occurred proximal to acorner where two surfaces of the structure or adjacent structures meetat an angle. It will be appreciated to those skilled in the art that aplurality of apertures 803 may be used to affix the plate-form 802 tothe structure. The use of a plurality of apertures 803 in conjunctiondistributes the load born by the fixation features. Certain embodimentsof a plate-form 802 has a length of 12.7 cm (5.0 in), width of 31.75 mm(1.25 in) and thickness of 6.35 mm (0.25 in). In such embodiments, aplate-form 802 further comprises a male threaded component 804 disposedcentrally to the width of the plate-form and 8.255 mm (0.325 in) from alongitudinal end of the plate-form, extending orthogonally from theplate-form.

Certain embodiments of the invention, as shown in FIGS. 10A and 10B,comprise a tension application component 1001 having at least twoparallel post structures 1002. The two parallel post structures 1002 aredisposed at an angle from a connecting body 1003. The tensionapplication component 1001 has an aperture 1004 located medial to thepost structures 1002. The aperture 1004 is also typically axiallyparallel to the post structures. The tension application component 1001distributes the load applied to the structure and provides apost-tensioning effect to a larger area. In certain embodiments, asecond tension application component, such as 101 a in FIG. 3, has apost feature attached to a tensioning mechanism, where the post-feature304 is disposed through the medially located aperture 1004. Certainembodiments of a tension application component as seen in FIG. 10Bcomprises a medially located aperture 1004 in a medially mounted tab1005 affixed to the tension application component. In such embodiments,a medially located aperture 1004 comprises a width of 12 mm (0.473 in)and length of 12.7 mm (0.5 in), the medially mounted tab 1005 having alength and width of 25.4 mm (1.00 in), and the tension applicationcomponent having an overall length of 30.5 cm (12.0 in).

Certain embodiments have a tension application component. In certainembodiments of, as shown in FIG. 11, the tension application componentcomprises a plate-form 1102. The plate-form 1102 affixes to a structureto apply tensile load to the structure at the desired location. Theplate-form 1102 can be affixed by masonry anchors or threaded featuresthrough apertures 1103 in the plate-form 1102, welding or other methodsknown to those skilled in the art. The plate-form 1102 further comprisesa fixation point 1104 configured to engage through a secondary tensionapplication component, such as having a loop, hook, post-like feature oraperture. In the case of the plate-form 1102 being fixated through theuse of a plurality of fasteners or anchors, this distributes any tensileloading applied to the fixation point such as when applyingpost-tensioning across a fissure or crack. The distributed load can alsoprovide tension between independent structures where other types oftension application components cannot. For example, post-like formscreate a higher localized concentration of stress and do not offer thenecessary structural stability to provide tension between independentstructures.

In certain embodiments of the invention such as that shown in FIG. 2,the apparatus comprises a tensioning mechanism, the tensioning mechanism102 having consistent cross-section. The tensioning mechanism 102 canhave female threaded features, 201 a and 201 b, at its distal ends. Thethreaded receptacles, 201 a and 201 b, having opposing threadingdirection. Thus, when engaged with rotationally constrained malethreaded features, the opposite threading direction allows both malethreaded features to be drawn toward the center of the tensioningmechanism 102 when rotated in a first direction and forces the malethreaded features away from center when rotated a second direction,opposite the first direction. Alternatively, it will be appreciated thatthe tensioning mechanism may have male threaded features and the tensionapplication components have female threaded features.

In certain embodiments, the tensioning mechanism has a torqueapplication feature. The torque application feature actuates thetensioning mechanism by to applying rotational forces to tensionapplication components. The torque application feature may havedifferent individual forms or a combination of forms as known to thoseskilled in the art. The profile of the tensioning mechanism may haveforms including but not limited to elliptical, circular, hexagonal,octagonal or square.

In certain embodiments the tensioning mechanism 102, such as that shownin FIG. 2, has at least one at least one torque application aperture202. The torque application aperture 202, passes through the tensioningmechanism perpendicular to the central axis of the mechanism typicallyintersecting the central axis of the tensioning mechanism 102. Thetorque application aperture 202 allows for torque application throughthe use of a rod or other shaft-like object. After torque application,it may be desired to dispose a rod in the torque application aperture202 to prevent counter-rotation by engaging the rod with the structure,such as concrete, to which an apparatus comprising a tensioningmechanism 102 is applied. It will be appreciated to those skilled in theart, that apertures 202 are typically be in a medial section of thetensioning mechanism 102. Furthermore, it may be desired to have aplurality of apertures. The additional apertures 202 can be radiallydisplaced from other apertures such as on 45-degree or 90-degreeincrements that allow for easier adjustment of the tensioning mechanism102 in tighter locations. The apertures 202 may be coplanar to the axisof the central axis. In certain embodiments, the apertures 202 may belocated on offset yet parallel planes perpendicular to the axis of thecentral axis of the tensioning mechanism 102.

In certain embodiments, the external profile of a tensioning devicecomprises a form with parallel exterior surfaces, such as a square,hexagonal or octagonal form, wherein the external profile may be usedfor the application of torque with a tool such as a wrench or otherstandard torque tool.

Embodiments of the invention disclosed herein may be used in a systemcomprising at least one tensioning mechanism and at least two tensionapplication components wherein the tensioning components areinterchangeably with a tensioning mechanism to allow systemcustomization for each application. In such an embodiment of a systemthe tension application components may have a threading to match thetensioning mechanism with right-hand or left-hand threads alternatively.It will be appreciated that a system comprising at least one tensioningmechanism and at least two tension application components may comprise afirst tension application component of a first type and a second tensionapplication component of a second type.

In the foregoing specification, specific embodiments have beendescribed. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the invention as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and all such modifications are intendedto be included within the scope of present teachings. The benefits,advantages, solutions to problems, and any element(s) that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as a critical, required, or essential features orelements of any or all the claims. The invention is defined solely bythe appended claims including any amendments made during the pendency ofthis application and all equivalents of those claims as issued.

What is claimed:
 1. An apparatus for applying tension to crackedconcrete surfaces comprising: a tensioning mechanism comprising aconstant cross-sectional profile, a first female threaded feature at afirst distal end of said tensioning mechanism, a second female threadedfeature at a second distal end of said tensioning mechanism, and atorque application feature located medially between said first andsecond female threaded features; a first tension application component,with a proximal end aligned with and proximate to said first distal endof said tensioning mechanism, said first tension application componenthaving a male threaded feature at said proximal end of said firsttension application component, said first tension application componenthaving at least one structure engaging feature located at a distal endof said first tension application component; a second tensionapplication component, with a proximal end aligned with and proximate tosaid second distal end of said tensioning mechanism, said second tensionapplication component having a male threaded feature at said proximalend of said second tension application component; said second tensionapplication component having at least one structure engaging featurelocated at a distal end of said second tension application component;said male threaded features of said first tension application componentand said second tension application component configured to engage withsaid female threaded features of said tensioning mechanism wherein therotation of the tensioning mechanism in a first direction causes saidfirst tension application component and said second tension applicationcomponents to retract toward a center of said tensioning mechanism androtation in a second direction causes the first and second components toprotract from the center of the tensioning mechanism; wherein actuationof said tensioning mechanism by rotation allows post-tensioning of astructure when said first tension application component and said secondtension application component are engaged with said structure.
 2. Theapparatus of claim 1, wherein said structure engaging feature of saidfirst tension application component and said second tension applicationcomponent are selected from the group consisting of: post-form,plate-form, loop, hook-form fixation point or aperture.
 3. The apparatusof claim 1, wherein the threading of said male threaded features andsaid female threaded features are of ANSI thread designation 3/8-16. 4.The apparatus of claim 1 wherein said apparatus comprises a materialcomposition comprising a steel alloy designated as a hot rolled andproof stressed alloy steel conforming to ASTM A722 CAN/CSA (G279-M1982).5. The apparatus of claim 1 wherein said apparatus comprises a materialcomposition comprising a steel allow designated as AISI 1144 compliant.6. The apparatus of claim 1 wherein said torque application featurecomprises a torque application aperture.